The invention relates to the spraying of plants and trees growing in parallel rows, in order to control insect pests and plant diseases. It relates particularly to the spraying of insecticides and fungicides over the entire height of these plants with a view to keeping them healthy from top to bottom. It relates moreover to the distribution of the necessary chemicals with the aid of pulsating air streams.
Spraying of insecticides and fungicides is nowadays mostly done from the air, or by means of stationary or movable sprayers, both methods causing the upper portions of the plants to be covered only, while most of the lower portions are not treated.
Spraying is either carried out by power sprayers, or by blower sprayers, both kinds being in about equal use today. Most power sprayers are of the hydraulic type in which spray pressure is built up by direct action of a pump on the liquid spray material. The pressure thus developed forces the liquid through nozzles which break it into spray of the desired droplet size and disperse it in the desired spray pattern. The pump and the nozzles are so designed that sufficient energy is imparted to the spray droplets to carry them from the nozzles to the surfaces to be treated.
Blower sprayers employ a blast of air to carry the chemical to the foliage to be treated. The typical concentrate sprayer of the blower type utilizes a low-pressure, low-volume pump serving to force the spray material to a fan where it is discharged into an air stream in small droplets by a number of nozzles. The air stream assists in breaking up the liquid into small particles, acts as a diluent to prevent the drops from coalescing and serves as the vehicle to carry the fine droplets to the plant surface. These blower sprayers are generally used in orchards for the purpose of spraying rows of trees from a relatively wide distance.
Distribution of liquid or dry chemicals by means of airplanes is costly, but does not require special tracks as required for travelling spraying equipment. On the other hand, distribution is not uniform due to changing wind direction and force, and the lower plant portions are not covered. Owing to the unequal distribution it usually becomes necessary to spray a larger volume of chemicals than with the other methods, in order to cover the plants with the required minimum.
Movable spraying equipment generally consists of a tractor-drawn or tractor-mounted transverse boom which carries a main pipe to which a plurality of spray nozzles or sprinklers are attached. The tractor moves at a velocity suitable for equal and sufficient spraying of chemicals on the plants over which the boom travels.
With plants growing in parallel, distanced rows it is possible to reach the lower branches and leaves by means of another known equipment: a horizontal boom and/or a main distribution pipe attached to a tractor, is provided with downwardly extending branches, each with a number of spray nozzles inserted on opposite sides. The branches are equidistantly spaced coextensive with the spacing of the planted rows, whereby every branch travels along the center line between the rows for the sake of equal liquid distribution. The spray nozzles are fed the chemical by means of a pump mounted on the equipment, usually driven from the tractor engine through a power-take-off.
It has also been proposed to distribute the chemicals by air streams expelled from pipes reaching downwardly between the rows of plants and provided with nozzles placed into the air jets or into the air openings in these pipes. Such implements have been described and claimed in U.S. Pat. No. 2,977,715 (Lindsay), in F 1,232,915, (Raynal) and in U.S. Pat. No. 3,943,688 (Billings).
Although the use of these chemical sprayers is preferable to spraying by aircraft, it has been shown that the spray created by the air streams does not reach the lower parts of the plants where the leaves are more exposed to attack by vermins and insects and, owing to the absence of sun radiation, are more liable to suffer from these attacks.
It is, therefore, the main object of the present invention to provide equipment for blower spraying of spaced rows of plants over their entire height, and especially the leaves in their lower portions close to the soil.
It is a further object not to spray both sides of each plant simultaneously, but one after the other by short bursts of air and chemicals which should stir the leaves and thus serve to distribute the chemicals from top to bottom of each plant.
It is still another object to spray fruit trees growing in rows by spraying equipment arranged close to the contours of these trees, again in bursts which follow each other at short intervals.
And it is a final object to provide equipment of simple design and at low costs.